Coenzyme Q10 is a benzoquinone derivative and known to be localized in the mitochondrion, lysosome, Golgi body, microsome, peroxisome, and cell membrane, among others, and involved, as constituents of the electron transport system, in ATP production and activation, in vivo antioxidant activity, and membrane stabilization; it is thus a substance indispensable for body function maintenance. Coenzyme Q10 is not only supplied from diets but also biosynthesized in the body, but it is known that the content thereof in the body is markedly decreased due to aging and various stresses to which the living body is subjected. In addition, the tissue coenzyme Q10 concentration is estimated to be decreased under conditions where peroxides are easily produced in the living body, such as hard exercises or overfatigue. Decrease in the coenzyme Q10 content in the body characteristically lead to decreased productivity of ATP, decreased cardiac function, decreased resistance to oxidation stress, and instability of biomembranes, thus being deleterious to health. Therefore, to make up for a shortage of coenzyme Q10 is advantageous for promoting energy production in mitochondria, enhancing the antioxidant capacity of the living body, and maintenance of homeostasis.
As for supplying coenzyme Q10, which is indispensable for maintaining biological functions but tends to be decreased and insufficient due to aging and stress as mentioned above, coenzyme Q10 has already been supplied exclusively as a drug or as a food supplement in the form of tablets or capsules. It is well known, however, that oral absorption of coenzyme Q10 is poor since the solubility thereof in water is very low. Thus, since coenzyme Q10 has very low solubility in water and alcohol, and also solubility in oils is low, emulsification thereof by an oil-in-water method is generally difficult. Furthermore, even if an oil-in-water emulsion can be temporarily obtained, there arises a problem that crystallization of coenzyme Q10 occurs in a short period which leads to emulsion breaking or solidification.
Patent Document 1 discloses a technology of using polyoxyethylene sorbitan monooleate for producing a beverage containing coenzyme Q10. The use of such an ethylene oxide-based surfactant has a risk for causing hemolysis, mucosal irritation, mucosal defect and the like and, in many cases, utilization thereof in food applications is actually hesitated.
Patent Document 2 discloses a technology of processing coenzyme Q10 with a high pressure using an emulsifier and polyhydric alcohol as aqueous solutions for dissolving liposoluble substances. Since the effect of preventing coenzyme Q10 crystallization is not sufficient, crystallization occurs and proceeds with time and therefore the oil-in-water emulsion cannot be maintained.
Patent Document 3 discloses a technology of using a medium chain fatty acid ester for preventing coenzyme Q10 crystallization and obtaining a stable oil-in-water emulsion. This technology requires use of a large amount of medium chain fatty acid ester for dissolving coenzyme Q10 and it is, however, difficult to obtain a product containing coenzyme Q10 at high ratio.
Patent Document 4 discloses a water-soluble composition containing coenzyme Q10 and oil. Since the effect of preventing coenzyme Q10 crystallization is not sufficient, crystallization occurs and proceeds with time and therefore the oil-in-water emulsion cannot be maintained.
Patent Document 5 discloses a liquid composition for drinking containing coenzyme Q10, a hydrophilic glycerol fatty acid ester and/or a hydrophilic sucrose fatty acid ester. The sucrose fatty acid ester used in this application is hydrophilic unlike the present invention, and the effect of preventing coenzyme Q10 crystallization is not considered at all, which comes into question in the case where high ratio of coenzyme Q10 is contained. Thus the stability of an oil-in-water emulsion is quite low.
Patent Document 6 discloses a technology of using polyglycerol with the average degree of polymerization of 10 together with a fatty acid monoester having 18 carbon atoms, and polyglycerol with the average degree of polymerization of 3 to 6 together with a fatty acid mono-, di-, tri-, or pentaester having 18 carbon atoms. The use of an unsaturated fatty acid such as oleic acid and linoleic acid is not suitable for long term preservation because of a worry of flavor deterioration due to oxidation deterioration and the like. Moreover, there may arise production difficulties in some cases, for example, high temperature is required in emulsification since a stearic acid ester itself has a high melting point.
Patent Document 7 discloses the effect of preventing coenzyme Q10 crystallization provided by using sterol, a sterol derivative, and a derivative having a skeleton similar to that of sterol, and a stable emulsion. However, utilization of such sterols in general foods is actually hesitated in many cases, and also, an acid resistance and heat resistance are not taken into consideration at all in this application.
Patent Document 8 discloses a coenzyme Q10-containing composition comprising a lipophilic polyhydric alcohol fatty acid ester and a hydrophilic polyhydric alcohol fatty acid ester, but there is no specific description regarding a lipophilic sucrose fatty acid ester, which is used in the present invention. Furthermore, stability of said composition is unclear so that no suggestion is given to the present invention by this application.    Patent Document 1: Japanese Kohyo Publication 2001-504343    Patent Document 2: Japanese Kokai Publication 2000-212066    Patent Document 3: Japanese Kokai Publication 2003-238396    Patent Document 4: Japanese Kokai Publication 2003-300870    Patent Document 5: Japanese Kokai Publication 2003-304847    Patent Document 6: Japanese Kokai Publication 2004-196781    Patent Document 7: Japanese Kokai Publication 2004-210669    Patent Document 8: International Publication WO04/064543